1. Field of the Invention
The present invention relates to a photoacid generator, a method for producing the photoacid generator, and a resist composition containing the photoacid generator. More particularly, the present invention relates to a photoacid generator which can maintain an appropriate contact angle at the time of ArF liquid immersion lithography, can reduce the defects occurring during liquid immersion lithography, has excellent solubility in resist solvents and excellent compatibility with resins, and can be produced by an efficient and simple method using an industrially easily available epoxy compound, a method for producing the photoacid generator, and a resist composition containing the photoacid generator.
2. Description of the Related Art
Chemically amplified positive resist compositions that are used in the semiconductor microprocessing including a lithographic process, include an acid generator containing a compound which generates acid when irradiated with light.
The acid generator absorbs the light used in semiconductor patterning processes. Onium salts that are mainly used as acid generators are such that the cationic moiety is decomposed into a radical form and comes to exist as a molecule of another form, and the anionic moiety generates acid, so that after irradiation, diffusion occurs on the resist film at the time of baking of the wafer.
During this process, the acid generator directly affects the resolution of the resist, the line edge roughness and the like by means of various factors such as the ability to absorb light, the acid production efficiency for the acid produced as a result of light absorption, the diffusion capability of the acid generated from the anion, and the strength of the acid generated from the anion.
Furthermore, in order to obtain excellent smoothness, the acid generator used in such chemically amplified resist materials needs to be uniformly dispersed in the resist composition. Therefore, the solubility of acid generators in resist solvents and compatibility thereof with resins are very important. However, conventional photoacid generators are not excellent in the solubility in solvents and the compatibility with resins, it is difficult to produce photoacid generators at low cost.